The present invention deals with mobility assistance. More particularly, the present invention deals with a vision assist device in the form of a head up display (HUD) for assisting mobility of a mobile body, such as a person, non-motorized vehicle or motor vehicle.
Driving a motor vehicle on the road, with a modicum of safety, can be accomplished if two different aspects of driving are maintained. The first is referred to as “collision avoidance” which means maintaining motion of a vehicle without colliding with other obstacles. The second aspect in maintaining safe driving conditions is referred to as “lane keeping” which means maintaining forward motion of a vehicle without erroneously departing from a given driving lane.
Drivers accomplish collision avoidance and lane keeping by continuously controlling vehicle speed, lateral position and heading direction by adjusting the acceleration and brake pedals, as well as the steering wheel. The ability to adequately maintain both collision avoidance and lane keeping is greatly compromised when the forward-looking visual field of a driver is obstructed. In fact, many researchers have concluded that the driver's ability to perceive the forward-looking visual field is the most essential input for the task of driving.
There are many different conditions which can obstruct (to varying degrees) the forward-looking visual field of a driver. For example, heavy snowfall, heavy rain, fog, smoke, darkness, blowing dust or sand, or any other substance or mechanism which obstructs (either partially or fully) the forward-looking visual field of a driver makes it difficult to identify obstacles and road boundaries which, in turn, compromises collision avoidance and lane keeping. Similarly, even on sunny, or otherwise clear days, blowing snow or complete coverage of the road by snow, may result in a loss of visual perception of the road. Such “white out” conditions are often encountered by snowplows working on highways, due to the nature of their task. The driver's forward-looking vision simply does not provide enough information to facilitate safe control of the vehicle. This can be exacerbated, particularly on snow removal equipment, because even on a relatively calm, clear day, snow can be blown up from the front or sides of snowplow blades, substantially obstructing the visual field of the driver.
Similarly, driving at night in heavy snowfall causes the headlight beams of the vehicle to be reflected into the driver's forward-looking view. Snow flakes glare brightly when they are illuminated at night and make the average brightness level perceived by the driver's eye higher than normal. This higher brightness level causes the iris to adapt to the increased brightness and, as a result, the eye becomes insensitive to the darker objects behind the glaring snowflakes, which are often vital to driving. Such objects can include road boundaries, obstacles, other vehicles, signs, etc.
Research has also been done which indicates that prolonged deprivation of visual stimulation can lead to confusion. For example, scientists believe that one third of human brain neurons are devoted to visual processing. Pilots, who are exposed to an empty visual field for longer than a certain amount of time, such as during high-altitude flight, or flight in thick fog, have a massive number of unstimulated visual neurons. This can lead to control confusion which makes it difficult for the pilot to control the vehicle. A similar condition can occur when attempting to navigate or plow a snowy road during daytime heavy snowfall in a featureless rural environment.
Many other environments are also plagued by poor visibility conditions. For instance, in military or other environments one may be moving through terrain at night, either in a vehicle or on foot, without the assistance of lights. Further, in mining environments or simply when driving on a dirt, sand or gravel surface particulate matter can obstruct vision. In water-going vehicles, it can be difficult to navigate through canals, around rocks, into a port, or through lock and dams because obstacles may be obscured by fog, below the water, or by other weather conditions. Similarly, surveyors may find it difficult to survey land with dense vegetation or rock formations which obstruct vision. People in non-motorized vehicles (such as in wheelchairs, on bicycles, on skis, etc. . . . can find themselves in these environments as well. All such environments, and many others, have visual conditions which act as a hindrance to persons working in, or moving through, those environments.